In the related art, when link switching is realized by implementing a redundant configuration in a network, the implementation is made using the same type of link. For example, for a redundant configuration using a packet network, switching of a link from a packet network to a packet network is implemented using a router. In addition, for example, for a redundant configuration using a time division-multiplexing (TDM) network, link switching from a TDM network to a TDM network is realized. Although a redundant network is also configured between interface converters in technology disclosed in Patent Document 1, both an active (ACT) system and a reserve system are implemented using a packet network.